U.S. patent number 8,938,988 [Application Number 13/541,392] was granted by the patent office on 2015-01-27 for multichannel heat exchanger with dissimilar flow.
This patent grant is currently assigned to Johnson Controls Technology Company. The grantee listed for this patent is Jose Ruel Yalung de la Cruz, William L. Kopko, Mustafa K. Yanik. Invention is credited to Jose Ruel Yalung de la Cruz, William L. Kopko, Mustafa K. Yanik.
United States Patent |
8,938,988 |
Yanik , et al. |
January 27, 2015 |
Multichannel heat exchanger with dissimilar flow
Abstract
Heating, ventilation, air conditioning, and refrigeration
(HVAC&R) systems and heat exchangers are provided that include
multichannel tube configurations designed to promote flow of
refrigerant within the multichannel tubes near the edges of the
tubes that are contacted first by an external fluid. The tube
configurations include flow paths of varying cross-sections,
spacings, and sizes. Flow control mechanisms, such as inserts,
blocking plates, sleeves, crimped sections, and crushed sections,
may be employed with the flow paths to favor flow near the edges of
the tubes that are contacted first by an external fluid.
Inventors: |
Yanik; Mustafa K. (York,
PA), Kopko; William L. (Jacobus, PA), de la Cruz; Jose
Ruel Yalung (Dover, PA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Yanik; Mustafa K.
Kopko; William L.
de la Cruz; Jose Ruel Yalung |
York
Jacobus
Dover |
PA
PA
PA |
US
US
US |
|
|
Assignee: |
Johnson Controls Technology
Company (Holland, MI)
|
Family
ID: |
41417286 |
Appl.
No.: |
13/541,392 |
Filed: |
July 3, 2012 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20120267086 A1 |
Oct 25, 2012 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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12200471 |
Aug 28, 2008 |
8234881 |
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Current U.S.
Class: |
62/515 |
Current CPC
Class: |
F28D
1/05383 (20130101); F28D 1/05341 (20130101); F28F
9/0243 (20130101); F28F 1/022 (20130101); F28F
9/0282 (20130101); F28F 1/025 (20130101); F25B
39/00 (20130101); F28F 2210/08 (20130101); F28F
2220/00 (20130101) |
Current International
Class: |
F25B
39/02 (20060101) |
Field of
Search: |
;62/498,515,324.1
;165/153,174,151,272 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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387330 |
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19740114 |
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Mar 1999 |
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DE |
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0219974 |
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Apr 1987 |
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EP |
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0583851 |
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Feb 1994 |
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EP |
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1426714 |
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Sep 2004 |
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EP |
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56130595 |
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Oct 1981 |
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JP |
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58045495 |
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Mar 1983 |
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JP |
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07190661 |
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Jul 1995 |
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JP |
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11083371 |
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Mar 1999 |
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JP |
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WO 02/103270 |
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Dec 2002 |
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WO |
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WO 2006/083435 |
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Aug 2006 |
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WO |
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WO 2006/083442 |
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Aug 2006 |
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WO |
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WO 2006/083450 |
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Aug 2006 |
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WO |
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2008/006423 |
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Jan 2008 |
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WO |
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Other References
Chinese Office Action and Search Report, Application No.
200910253039.3, issued Aug. 3, 2012. cited by applicant.
|
Primary Examiner: Jules; Frantz
Assistant Examiner: Duke; Emmanuel
Attorney, Agent or Firm: Fletcher Yoder, P.C.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a divisional of U.S. patent application Ser.
No. 12/200,471, filed Aug. 28, 2008, entitled "MULTICHANNEL HEAT
EXCHANGER WITH DISSIMILAR FLOW", which is hereby incorporated by
reference.
Claims
The invention claimed is:
1. A heat exchanger comprising: a first manifold; a second
manifold; a plurality of multichannel tubes extending lengthwise
between and in fluid communication with the first and second
manifolds, the plurality of multichannel tubes being configured to
receive an external fluid flowing across the width of each
multichannel tube from a leading edge to a trailing edge and
configured to flow an internal fluid along the length of each
multichannel tube such that the internal fluid exchanges heat with
the external fluid and a vapor quality of the internal fluid
changes as it progresses along the length; a plurality of generally
parallel flow paths disposed within each multichannel tube and
extending lengthwise through each multichannel tube; and a flow
control mechanism included within at least one multichannel tube,
the flow control mechanism being configured to allow more of the
internal fluid to flow near the leading edge than near the trailing
edge of the at least one multichannel tube, wherein the flow
control mechanism includes a crimped flow path disposed near the
trailing edge and an uncrimped flow path disposed near the leading
edge.
2. The heat exchanger of claim 1, wherein the crimped flow path has
a uniform cross-section across the length of the at least one
multichannel tube.
3. The heat exchanger of claim 1, wherein the flow control
mechanism includes a crushed flow path disposed near the trailing
edge and an uncrushed flow path disposed near the leading edge.
4. The heat exchanger of claim 1, wherein the flow control
mechanism disposed near a lengthwise end of the at least one
multichannel tube containing the internal fluid with a lower vapor
quality relative to an opposite lengthwise end of the at least one
multichannel tube.
5. A heat exchanger comprising: a first manifold; a second
manifold; a plurality of multichannel tubes in fluid communication
with the first and second manifolds, the plurality of multichannel
tubes being configured to receive an external fluid flowing across
a width dimension extending from a leading edge to a trailing edge;
a plurality of generally parallel flow paths disposed within each
of the plurality of multichannel tubes extending lengthwise through
each of the plurality of multichannel tubes, each flow path being
configured to flow an internal fluid such that the internal fluid
exchanges heat with the external fluid and a vapor quality of the
internal fluid changes as it progresses lengthwise through each of
the plurality of multichannel tubes; a first flow path of the
plurality of generally parallel flow paths disposed near the
leading edge; a second flow path disposed near the trailing edge;
and a crimp in the second flow path disposed near an end of the
second flow path containing the internal fluid with a lowest vapor
quality relative to other portions of the second flow path, wherein
the crimp is configured to manage flow by reducing the size of the
second flow path such that the second flow path is smaller than the
first flow path.
6. The heat exchanger of claim 5, wherein the first flow path has a
uniform cross-section across the length of the first flow path.
7. The heat exchanger of claim 5, comprising fins disposed between
the plurality of multichannel tubes.
8. The heat exchanger of claim 5, wherein the plurality of
generally parallel flow paths is configured to allow more of the
internal fluid to flow within each of the plurality of multichannel
tubes near the leading edge relative to an amount flowing near the
trailing edge.
9. A heat exchanger comprising: a first manifold; a second
manifold; a plurality of multichannel tubes in fluid communication
with the first and second manifolds, the plurality of multichannel
tubes being configured to receive an external fluid flowing across
a width dimension extending from a leading edge to a trailing edge;
a plurality of generally parallel flow paths disposed within each
of the plurality of multichannel tubes and extending lengthwise
through each of the plurality of multichannel tubes, wherein a
distance between each of the plurality of generally parallel flow
paths increases along the width dimension from the leading edge to
the trailing edge; a first flow path disposed near the leading edge
of a first multichannel tube of the plurality of multichannel
tubes; and a second flow path disposed near the trailing edge of
the first multichannel tube, the second flow path having an opening
that is partially obstructed by a flow control mechanism to reduce
a size of the opening such that the second flow path is smaller
than the first flow path, wherein the flow control mechanism
includes a crimped flow path.
Description
BACKGROUND
The invention relates generally to multichannel heat exchangers
with dissimilar flow across the width of multichannel tubes.
Heat exchangers are used in heating, ventilation, air conditioning,
and refrigeration (HVAC&R) systems. Multichannel heat
exchangers generally include multichannel tubes for flowing
refrigerant through the heat exchanger. Each multichannel tube may
contain several individual flow channels, or paths. Fins may be
positioned between the tubes to facilitate heat transfer between
refrigerant contained within the flow paths and an external fluid
passing over the tubes. Moreover, multichannel heat exchangers may
be used in small tonnage systems, such as residential systems, or
in large tonnage systems, such as industrial chiller systems.
The transfer of heat within multichannel heat exchangers is
generally driven by flow of an external fluid passing through the
heat exchanger. Typically, as the fluid passes through the heat
exchanger (i.e., over the tubes), the fluid contacts the individual
multichannel tubes and flows across each tube, contacting first a
leading edge of the tube, flowing across the width of the tube, and
contacting last a trailing edge of the tube. Heat transfer between
the external fluid and the refrigerant is dependent on, among other
things, the temperature difference between the external fluid
flowing across the multichannel tubes and the refrigerant flowing
inside the multichannel tubes. For example, in an evaporator, an
external fluid, such as air, may flow over the multichannel tubes.
The refrigerant flowing inside the multichannel tubes is generally
cooler than the air and, therefore, absorbs heat from the air. The
exchange of heat may produce cooled air exiting the heat exchanger
and warmed refrigerant flowing within the heat exchanger. In an
example employing a condenser, an external fluid, such as air, may
flow over multichannel tubes containing a refrigerant that is
generally warmer than the air. As the air flows across the tubes,
the internal refrigerant transfers heat to the air. The exchange of
heat may produce warmed air exiting the heat exchanger and cooled
refrigerant flowing within the heat exchanger.
In both evaporator and condenser applications, the greatest
temperature difference between the external fluid flowing across
the tubes and the internal refrigerant flowing within the tubes
generally exists at the leading edge of the tubes. As the external
fluid flows across the width of the tubes, heat transfer occurs
causing the external fluid temperature to approach the temperature
of the internal refrigerant. Therefore, less heat transfer may
occur at the trailing edge of the tubes because the external fluid
has already absorbed or transferred some heat to or from the
internal refrigerant.
SUMMARY
The present invention relates to a heat exchanger with a first
manifold, a second manifold, a plurality of multichannel tubes in
fluid communication with the manifolds, and a plurality of
generally parallel flow paths disposed lengthwise within each
multichannel tube. The multichannel tubes are configured to receive
an external fluid flowing across a width dimension extending from a
leading edge to a trailing edge, and the flow paths are configured
to favor flow of an internal fluid within each multichannel tube
near the leading edge. A flow control mechanism may be included in
a multichannel tube near the end of the tube containing the lowest
vapor quality.
The present invention also relates to a multichannel tube for a
heat exchanger. The tube includes a leading edge configured to be
contacted by an external fluid, a trailing edge configured to by
contacted by the external fluid after contact with the leading
edge, and two or more generally parallel flow paths extending along
the length of the tube. The flow paths are configured to effect a
first flow of an internal fluid within the tube near the leading
edge and a second flow of the internal fluid within the tube near
the trailing edge. The second flow is reduced with respect to the
first flow.
The present invention further relates to systems and methods
employing the heat exchangers and multichannel tubes.
DRAWINGS
FIG. 1 is perspective view of an exemplary residential air
conditioning or heat pump system of the type that might employ a
heat exchanger in accordance with the present techniques.
FIG. 2 is a partially exploded view of the outside unit of the
system of FIG. 1, with an upper assembly lifted to expose certain
of the system components.
FIG. 3 is a perspective view of an exemplary commercial or
industrial HVAC&R system that employs a chiller and air
handlers to cool a building and that may also employ heat
exchangers in accordance with the present techniques.
FIG. 4 is a diagrammatical overview of an exemplary air
conditioning system that may employ one or more heat exchangers in
accordance with the present techniques.
FIG. 5 is a diagrammatical overview of an exemplary heat pump
system that may employ one or more heat exchangers in accordance
with the present techniques.
FIG. 6 is a perspective view of an exemplary heat exchanger
containing multichannel tubes in accordance with the present
techniques.
FIG. 7 is a detailed perspective view of a section of multichannel
tubes and fins employed in the heat exchanger of FIG. 6.
FIG. 8 is a partially exploded detailed perspective view of a
portion of the heat exchanger of FIG. 6 illustrating component
parts.
FIG. 9 is a sectional view of an exemplary multichannel tube with
varying flow areas separated by a constant spacing depicted below a
corresponding temperature profile across the width of the
multichannel tube functioning in a condenser in accordance with the
present techniques.
FIG. 10 is a sectional view of the exemplary multichannel tube
shown in FIG. 9 depicted below a corresponding temperature profile
across the width of the multichannel tube functioning in an
evaporator in accordance with the present techniques.
FIG. 11 is a sectional view of an exemplary multichannel tube that
may be employed in the heat exchanger of FIG. 6 illustrating flow
paths with varying flow areas separated by a constant spacing.
FIG. 12 is a sectional view of an alternate exemplary multichannel
tube illustrating flow paths with varying flow areas separated by a
constant spacing in accordance with the present techniques.
FIG. 13 is a sectional view of an exemplary multichannel tube
illustrating flow paths of a constant size separated by a
progressive spacing.
FIG. 14 is a sectional view of an alternate exemplary multichannel
tube illustrating flow paths of a constant size separated by a
progressive spacing.
FIG. 15 is a sectional view of an exemplary multichannel tube
illustrating flow paths of varying sizes separated by a progressive
spacing.
FIG. 16 is a sectional view of an exemplary multichannel tube
illustrating flow paths of varying cross-sections and sizes
separated by a progressive spacing.
FIG. 17 is a detailed perspective view of an exemplary multichannel
tube including flow control mechanisms inserted within the flow
paths.
FIG. 18 is a detailed perspective view of a flow control mechanism
employed in FIG. 17.
FIG. 19 is a detailed perspective view of an alternate flow control
mechanism that may be inserted into an exemplary multichannel
tube.
FIG. 20 is a detailed perspective view of an exemplary multichannel
tube including the flow control mechanism of FIG. 19 inserted
within flow paths.
FIG. 21 is a detailed perspective view of a bracket that may be
used to insert the flow control mechanisms of FIG. 20.
FIG. 22 is an exploded perspective view of an alternate flow
control mechanism that may be employed with an exemplary
multichannel tube.
FIG. 23 is a detailed perspective view of the flow control
mechanism illustrated in FIG. 22 disposed on the end of a
multichannel tube.
FIG. 24 is a detailed perspective view of an alternate flow control
mechanism disposed on the end of a multichannel tube.
FIG. 25 is a detailed perspective view of yet another flow control
mechanism disposed on the end of a multichannel tube.
FIG. 26 is an exploded perspective view of an alternate flow
control mechanism that may encapsulate the end of a multichannel
tube.
FIG. 27 is a detailed perspective view of an exemplary multichannel
tube including a flow control mechanism that encompasses a section
of the tube.
FIG. 28 is a detailed perspective view of an alternate flow control
mechanism that may be included within a section of an exemplary
multichannel tube.
DETAILED DESCRIPTION
FIGS. 1 through 3 depict exemplary applications for heat
exchangers. Such systems, in general, may be applied in a range of
settings, both within the HVAC&R field and outside of that
field. In presently contemplated applications, however, heat
exchanges may be used in residential, commercial, light industrial,
industrial, and in any other application for heating or cooling a
volume or enclosure, such as a residence, building, structure, and
so forth. Moreover, the heat exchanges may be used in industrial
applications, where appropriate, for basic refrigeration and
heating of various fluids. FIG. 1 illustrates a residential heating
and cooling system. In general, a residence 10, will include
refrigerant conduits 12 that operatively couple an indoor unit 14
to an outdoor unit 16. Indoor unit 14 may be positioned in a
utility room, an attic, a basement, and so forth. Outdoor unit 16
is typically situated adjacent to a side of residence 10 and is
covered by a shroud to protect the system components and to prevent
leaves and other contaminants from entering the unit. Refrigerant
conduits 12 transfer refrigerant between indoor unit 14 and outdoor
unit 16, typically transferring primarily liquid refrigerant in one
direction and primarily vaporized refrigerant in an opposite
direction.
When the system shown in FIG. 1 is operating as an air conditioner,
a coil in outdoor unit 16 serves as a condenser for recondensing
vaporized refrigerant flowing from indoor unit 14 to outdoor unit
16 via one of the refrigerant conduits 12. In these applications, a
coil of the indoor unit, designated by the reference numeral 18,
serves as an evaporator coil. Evaporator coil 18 receives liquid
refrigerant (which may be expanded by an expansion device, not
shown) and evaporates the refrigerant before returning it to
outdoor unit 16.
Outdoor unit 16 draws in environmental air through its sides as
indicated by the arrows directed to the sides of the unit, forces
the air through the outer unit coil by a means of a fan (not
shown), and expels the air as indicated by the arrows above the
outdoor unit. When operating as an air conditioner, the air is
heated by the condenser coil within the outdoor unit and exits the
top of the unit at a temperature higher than it entered the sides.
Air is blown over indoor coil 18 and is then circulated through
residence 10 by means of ductwork 20, as indicated by the arrows
entering and exiting ductwork 20. The overall system operates to
maintain a desired temperature as set by a thermostat 22 or other
control device or system (e.g., a computer, digital or analog
controller, etc.). When the temperature sensed inside the residence
is higher than the set point on the thermostat (plus a small
amount), the air conditioner will become operative to refrigerate
additional air for circulation through the residence. When the
temperature reaches the set point (minus a small amount), the unit
will stop the refrigeration cycle temporarily.
When the unit in FIG. 1 operates as a heat pump, the roles of the
coils are simply reversed. That is, the coil of outdoor unit 16
will serve as an evaporator to evaporate refrigerant and thereby
cool air entering outdoor unit 16 as the air passes over the
outdoor unit coil. Indoor coil 18 will receive a stream of air
blown over it and will heat the air by condensing a
refrigerant.
FIG. 2 illustrates a partially exploded view of one of the units
shown in FIG. 1, in this case outdoor unit 16. In general, the unit
may be thought of as including an upper assembly 24 made up of a
shroud, a fan assembly, a fan drive motor, and so forth. In the
illustration of FIG. 2, the fan and fan drive motor are not visible
because they are hidden by the surrounding shroud. An outdoor coil
26 is housed within this shroud and is generally deposed to
surround or at least partially surround other system components,
such as a compressor, an expansion device, a control circuit.
FIG. 3 illustrates another exemplary application, in this case an
HVAC&R system for building environmental management. A building
28 is cooled by a system that includes a chiller 30, which is
typically disposed on or near the building, or in an equipment room
or basement. Chiller 30 is an air-cooled device that implements a
refrigeration cycle to cool water. The water is circulated to
building 28 through water conduits 32. The water conduits are
routed to air handlers 34 at individual floors or sections of the
building. The air handlers are also coupled to ductwork 36 that is
adapted to blow air from an outside intake 38.
Chiller 30, which includes heat exchangers for both evaporating and
condensing a refrigerant as described above, cools water that is
circulated to the air handlers. Air blown over additional coils
that receive the water in the air handlers causes the water to
increase in temperature and the circulated air to decrease in
temperature. The cooled air is then routed to various locations in
the building via additional ductwork. Ultimately, distribution of
the air is routed to diffusers that deliver the cooled air to
offices, apartments, hallways, and any other interior spaces within
the building. In many applications, thermostats or other command
devices (not shown in FIG. 3) will serve to control the flow of air
through and from the individual air handlers and ductwork to
maintain desired temperatures at various locations in the
structure.
FIG. 4 illustrates an air conditioning system 40, which may employ
multichannel tube heat exchangers. Refrigerant flows through system
40 within closed refrigeration loop 42. The refrigerant may be any
fluid that absorbs and extracts heat. For example, the refrigerant
may be hydrofluorocarbon (HFC) based R-410A, R-407C, or R-134a, or
it may be carbon dioxide (R-744) or ammonia (R-717). Air
conditioning system 40 includes control devices 44 that enable the
system to cool an environment to a prescribed temperature.
System 40 cools an environment by cycling refrigerant within closed
refrigeration loop 42 through a condenser 46, a compressor 48, an
expansion device 50, and an evaporator 52. The refrigerant enters
condenser 46 as a high pressure and temperature vapor and flows
through the multichannel tubes of the condenser. A fan 54, which is
driven by a motor 56, draws air across the multichannel tubes. The
fan may push or pull air across the tubes. As the air flows across
the tubes, heat transfers from the refrigerant vapor to the air,
producing heated air 58 and causing the refrigerant vapor to
condense into a liquid. The liquid refrigerant then flows into an
expansion device 50 where the refrigerant expands to become a low
pressure and temperature liquid. Typically, expansion device 50
will be a thermal expansion valve (TXV); however, according to
other exemplary embodiments, the expansion device may be an orifice
or a capillary tube. After the refrigerant exits the expansion
device, some vapor refrigerant may be present in addition to the
liquid refrigerant.
From expansion device 50, the refrigerant enters evaporator 52 and
flows through the evaporator multichannel tubes. A fan 60, which is
driven by a motor 62, draws air across the multichannel tubes. As
the air flows across the tubes, heat transfers from the air to the
refrigerant liquid, producing cooled air 64 and causing the
refrigerant liquid to boil into a vapor. According to certain
embodiments, the fan may be replaced by a pump that draws fluid
across the multichannel tubes.
The refrigerant then flows to compressor 48 as a low pressure and
temperature vapor. Compressor 48 reduces the volume available for
the refrigerant vapor, consequently, increasing the pressure and
temperature of the vapor refrigerant. The compressor may be any
suitable compressor such as a screw compressor, reciprocating
compressor, rotary compressor, swing link compressor, scroll
compressor, or turbine compressor. Compressor 48 is driven by a
motor 66 that receives power from a variable speed drive (VSD) or a
direct AC or DC power source. According to an exemplary embodiment,
motor 66 receives fixed line voltage and frequency from an AC power
source although in certain applications the motor may be driven by
a variable voltage or frequency drive. The motor may be a switched
reluctance (SR) motor, an induction motor, an electronically
commutated permanent magnet motor (ECM), or any other suitable
motor type. The refrigerant exits compressor 48 as a high
temperature and pressure vapor that is ready to enter the condenser
and begin the refrigeration cycle again.
The control devices 44, which include control circuitry 68, an
input device 70, and a temperature sensor 72, govern the operation
of the refrigeration cycle. Control circuitry 68 is coupled to the
motors 56, 62, and 66 that drive condenser fan 54, evaporator fan
60, and compressor 48, respectively. Control circuitry 68 uses
information received from input device 70 and sensor 72 to
determine when to operate the motors 56, 62, and 66 that drive the
air conditioning system. In certain applications, the input device
may be a conventional thermostat. However, the input device is not
limited to thermostats, and more generally, any source of a fixed
or changing set point may be employed. These may include local or
remote command devices, computer systems and processors, and
mechanical, electrical and electromechanical devices that manually
or automatically set a temperature-related signal that the system
receives. For example, in a residential air conditioning system,
the input device may be a programmable 24-volt thermostat that
provides a temperature set point to the control circuitry. Sensor
72 determines the ambient air temperature and provides the
temperature to control circuitry 68. Control circuitry 68 then
compares the temperature received from the sensor to the
temperature set point received from the input device. If the
temperature is higher than the set point, control circuitry 68 may
turn on motors 56, 62, and 66 to run air conditioning system 40.
The control circuitry may execute hardware or software control
algorithms to regulate the air conditioning system. According to
exemplary embodiments, the control circuitry may include an analog
to digital (A/D) converter, a microprocessor, a non-volatile
memory, and an interface board. Other devices may, of course, be
included in the system, such as additional pressure and/or
temperature transducers or switches that sense temperatures and
pressures of the refrigerant, the heat exchangers, the inlet and
outlet air, and so forth.
FIG. 5 illustrates a heat pump system 74 that may employ
multichannel tube heat exchangers. Because the heat pump may be
used for both heating and cooling, refrigerant flows through a
reversible refrigeration/heating loop 76. The refrigerant may be
any fluid that absorbs and extracts heat. The heating and cooling
operations are regulated by control devices 78.
Heat pump system 74 includes an outside coil 80 and an inside coil
82 that both operate as heat exchangers. The coils may function
either as an evaporator or a condenser depending on the heat pump
operation mode. For example, when heat pump system 74 is operating
in cooling (or "AC") mode, outside coil 80 functions as a
condenser, releasing heat to the outside air, while inside coil 82
functions as an evaporator, absorbing heat from the inside air.
When heat pump system 74 is operating in heating mode, outside coil
80 functions as an evaporator, absorbing heat from the outside air,
while inside coil 82 functions as a condenser, releasing heat to
the inside air. A reversing valve 84 is positioned on reversible
loop 76 between the coils to control the direction of refrigerant
flow and thereby to switch the heat pump between heating mode and
cooling mode.
Heat pump system 74 also includes two metering devices 86 and 88
for decreasing the pressure and temperature of the refrigerant
before it enters the evaporator. The metering devices also regulate
the refrigerant flow entering the evaporator so that the amount of
refrigerant entering the evaporator equals, or approximately
equals, the amount of refrigerant exiting the evaporator. The
metering device used depends on the heat pump operation mode. For
example, when heat pump system 74 is operating in cooling mode,
refrigerant bypasses metering device 86 and flows through metering
device 88 before entering inside coil 82, which acts as an
evaporator. In another example, when heat pump system 74 is
operating in heating mode, refrigerant bypasses metering device 88
and flows through metering device 86 before entering outside coil
80, which acts as an evaporator. According to other exemplary
embodiments, a single metering device may be used for both heating
mode and cooling mode. The metering devices typically are thermal
expansion valves (TXV), but also may be orifices or capillary
tubes.
The refrigerant enters the evaporator, which is outside coil 80 in
heating mode and inside coil 82 in cooling mode, as a low
temperature and pressure liquid. Some vapor refrigerant also may be
present as a result of the expansion process that occurs in
metering device 86 or 88. The refrigerant flows through
multichannel tubes in the evaporator and absorbs heat from the air
changing the refrigerant into a vapor. In cooling mode, the indoor
air flowing across the multichannel tubes also may be dehumidified.
The moisture from the air may condense on the outer surface of the
multichannel tubes and consequently be removed from the air.
After exiting the evaporator, the refrigerant passes through
reversing valve 84 and into a compressor 90. Compressor 90
decreases the volume of the refrigerant vapor, thereby, increasing
the temperature and pressure of the vapor. The compressor may be
any suitable compressor such as a screw compressor, reciprocating
compressor, rotary compressor, swing link compressor, scroll
compressor, or turbine compressor.
From compressor 90, the increased temperature and pressure vapor
refrigerant flows into a condenser, the location of which is
determined by the heat pump mode. In cooling mode, the refrigerant
flows into outside coil 80 (acting as a condenser). A fan 92, which
is powered by a motor 94, draws air across the multichannel tubes
containing refrigerant vapor. According to certain exemplary
embodiments, the fan may be replaced by a pump that draws fluid
across the multichannel tubes. The heat from the refrigerant is
transferred to the outside air causing the refrigerant to condense
into a liquid. In heating mode, the refrigerant flows into inside
coil 82 (acting as a condenser). A fan 96, which is powered by a
motor 98, draws air across the multichannel tubes containing
refrigerant vapor. The heat from the refrigerant is transferred to
the inside air causing the refrigerant to condense into a
liquid.
After exiting the condenser, the refrigerant flows through the
metering device (86 in heating mode and 88 in cooling mode) and
returns to the evaporator (outside coil 80 in heating mode and
inside coil 82 in cooling mode) where the process begins again.
In both heating and cooling modes, a motor 100 drives compressor 90
and circulates refrigerant through reversible refrigeration/heating
loop 76. The motor may receive power either directly from an AC or
DC power source or from a variable speed drive (VSD). The motor may
be a switched reluctance (SR) motor, an induction motor, an
electronically commutated permanent magnet motor (ECM), or any
other suitable motor type.
The operation of motor 100 is controlled by control circuitry 102.
Control circuitry 102 receives information from an input device 104
and sensors 106, 108, and 110 and uses the information to control
the operation of heat pump system 74 in both cooling mode and
heating mode. For example, in cooling mode, input device 104
provides a temperature set point to control circuitry 102. Sensor
110 measures the ambient indoor air temperature and provides it to
control circuitry 102. Control circuitry 102 then compares the air
temperature to the temperature set point and engages compressor
motor 100 and fan motors 94 and 98 to run the cooling system if the
air temperature is above the temperature set point. In heating
mode, control circuitry 102 compares the air temperature from
sensor 110 to the temperature set point from input device 104 and
engages motors 94, 98, and 100 to run the heating system if the air
temperature is below the temperature set point.
Control circuitry 102 also uses information received from input
device 104 to switch heat pump system 74 between heating mode and
cooling mode. For example, if input device 104 is set to cooling
mode, control circuitry 102 will send a signal to a solenoid 112 to
place reversing valve 84 in an air conditioning position 114.
Consequently, the refrigerant will flow through reversible loop 76
as follows: the refrigerant exits compressor 90, is condensed in
outside coil 80, is expanded by metering device 88, and is
evaporated by inside coil 82. If the input device is set to heating
mode, control circuitry 102 will send a signal to solenoid 112 to
place reversing valve 84 in a heat pump position 116. Consequently,
the refrigerant will flow through the reversible loop 76 as
follows: the refrigerant exits compressor 90, is condensed in
inside coil 82, is expanded by metering device 86, and is
evaporated by outside coil 80.
The control circuitry may execute hardware or software control
algorithms to regulate heat pump system 74. According to exemplary
embodiments, the control circuitry may include an analog to digital
(A/D) converter, a microprocessor, a non-volatile memory, and an
interface board.
The control circuitry also may initiate a defrost cycle when the
system is operating in heating mode. When the outdoor temperature
approaches freezing, moisture in the outside air that is directed
over outside coil 80 may condense and freeze on the coil. Sensor
106 measures the outside air temperature, and sensor 108 measures
the temperature of outside coil 80. These sensors provide the
temperature information to the control circuitry which determines
when to initiate a defrost cycle. For example, if either sensor 106
or 108 provides a temperature below freezing to the control
circuitry, system 74 may be placed in defrost mode. In defrost
mode, solenoid 112 is actuated to place reversing valve 84 in air
conditioning position 114, and motor 94 is shut off to discontinue
air flow over the multichannel tubes. System 74 then operates in
cooling mode until the increased temperature and pressure
refrigerant flowing through outside coil 80 defrosts the coil. Once
sensor 108 detects that coil 80 is defrosted, control circuitry 102
returns the reversing valve 84 to heat pump position 146. As will
be appreciated by those skilled in the art, the defrost cycle can
be set to occur at many different time and temperature
combinations.
FIG. 6 is a perspective view of an exemplary heat exchanger that
may be used in air conditioning system 40, shown in FIG. 4, or heat
pump system 70, shown in FIG. 5. The exemplary heat exchanger may
be a condenser 46, an evaporator 52, an outside coil 80, or an
inside coil 82, as shown in FIGS. 4 and 5. It should be noted that
in similar or other systems, the heat exchanger may be used as part
of a chiller or in any other heat exchanging application. The heat
exchanger includes manifolds 120 and 122 that are connected by
multichannel tubes 124. Although 30 tubes are shown in FIG. 6, the
number of tubes may vary. The manifolds and tubes may be
constructed of aluminum or any other material that promotes good
heat transfer. Refrigerant flows from manifold 120 through a set of
first tubes 126 to manifold 122. The refrigerant then returns to
manifold 120 in an opposite direction through a set of second tubes
128. The first tubes may have the same configuration as the second
tubes or the first tubes may have a different configuration from
the second tubes. According to other exemplary embodiments, the
heat exchanger may be rotated approximately 90 degrees so that the
multichannel tubes run vertically between a top manifold and a
bottom manifold. Furthermore, the heat exchanger may be inclined at
an angle relative to the vertical. Although the multichannel tubes
are depicted as having an oblong shape, the tubes may be any shape,
such as tubes with a cross-section in the form of a rectangle,
square, circle, oval, ellipse, triangle, trapezoid, or
parallelogram. According to exemplary embodiments, the tubes may
have an oblong cross-sectional shape with a height ranging from 0.5
mm to 3 mm and a width ranging from 18 mm to 25 mm. It should also
be noted that the heat exchanger may be provided in a single plane
or slab, or may include bends, corners, contours, and so forth.
According to certain exemplary embodiments, the construction of the
first tubes may differ from the construction of the second tubes.
Tubes may also differ within each section. For example, the tubes
may all have identical cross-sections, where the tubes in the first
section may be rectangular while the tubes in the second section
are oval. The internal construction of the tubes as described below
with regard to FIGS. 11 through 28 may also vary within and across
tube sections such that the internal flow paths are of different
configurations or have various flow control mechanisms included in
them.
Refrigerant enters the heat exchanger through an inlet 130 and
exits the heat exchanger through an outlet 132. Although FIG. 6
depicts the inlet at the top of manifold 120 and the outlet at the
bottom of manifold 120, the inlet and outlet positions may be
interchanged so that the fluid enters at the bottom and exits at
the top. The fluid also may enter and exit the manifold from
multiple inlets and outlets positioned on bottom, side, or top
surfaces of the manifold. Baffles 134 separate the inlet and outlet
portions of manifold 120. Although a double baffle 134 is
illustrated, any number of one or more baffles may be employed to
create separation of the inlet and outlet portions. It should also
be noted that according to other exemplary embodiments, the inlet
and outlet may be contained on separate manifolds, eliminating the
need for a baffle.
Fins 136 are located between multichannel tubes 124 to promote the
transfer of heat between the tubes and the environment. According
to an exemplary embodiment, the fins are constructed of aluminum,
brazed or otherwise joined to the tubes, and disposed generally
perpendicular to the flow of refrigerant. However, according to
other exemplary embodiments, the fins may be made of other
materials that facilitate heat transfer and may extend parallel or
at varying angles with respect to the flow of the refrigerant. The
fins may be louvered fins, corrugated fins, or any other suitable
type of fin.
When an external fluid, such as air, flows across multichannel
tubes 124, as generally indicated by arrows 138, heat transfer
occurs between the refrigerant flowing within tubes 124 and the
external fluid. Typically, the external fluid, shown here as air,
flows through fins 136 contacting the upper and lower sides of
multichannel tubes 124. The external fluid first contacts
multichannel tubes 124 at a leading edge 140, then flows across the
width of the tubes, and lastly contacts a trailing edge 142 of the
tubes. As the external fluid flows across the tubes, heat is
transferred to and from the tubes to the external fluid. For
example, in a condenser, the external fluid is generally cooler
than the fluid flowing within the multichannel tubes. As the
external fluid contacts the leading edge of a multichannel tube,
heat is transferred from the refrigerant within the multichannel
tube to the external fluid. Consequently, the external fluid is
heated as it passes over the multichannel tubes and the refrigerant
flowing within the multichannel tubes is cooled. In an evaporator,
the external fluid generally has a temperature higher than the
refrigerant flowing within the multichannel tubes. Consequently, as
the external fluid contacts the leading edge of the multichannel
tubes, heat is transferred from the external fluid to the
refrigerant flowing in the tubes to heat the refrigerant. The
external fluid leaving the multichannel tubes is then cooled
because the heat has been transferred to the refrigerant.
FIG. 7 is a detailed perspective view of tubes 124 and fins 136
illustrated in FIG. 6, sectioned through the tubes and fins. An
external fluid, indicated generally by arrows 138, flows through
fins 136 and across a width A of tubes 124, contacting the upper
and lower surfaces of the tubes. Fins 136 function to promote heat
transfer between the refrigerant flowing within tubes 124 and the
external fluid flowing across the tubes. The external fluid, shown
here as air, first contacts a leading edge 140, flows across width
A of a tube 124, and lastly contacts in a trailing edge 142.
Refrigerant flows within multichannel tubes 124 through flow paths
144 in a direction generally perpendicular to the direction of air
flow 138. Each tube 124 has a width A across which the external
fluid 138 passes. Each tube 124 also has a height B, which is
typically much smaller than width A. As the external fluid flows
across width A of the multichannel tubes, heat is transferred
between the refrigerant and the external fluid. The temperature
difference between the refrigerant and the external fluid is
typically the greatest at leading edge 140 because no, or minimal,
heat transfer has occurred between the external fluid and the
refrigerant. Specifically, as the external fluid flows across tube
width A, the fluid absorbs or transfers heat from or to the
refrigerant within the tubes. Because of the heat transfer, the
temperature of the external fluid approaches the temperature of the
refrigerant as the fluid travels across the width. Therefore, more
heat transfer may occur at leading edge 140 of the tubes (where the
temperature difference is generally greatest) than at trailing edge
142 (where the temperature difference is generally smallest).
FIG. 8 illustrates certain components of the heat exchanger of FIG.
6 in a somewhat more detailed exploded view. Each manifold
(manifold 120 being shown in FIG. 8) is a tubular structure with
open ends that are closed by a cap 146. Openings, or apertures, 148
are formed in the manifolds, such as by conventional piercing
operations. Multichannel tubes 124 may then be inserted into
openings 148 in a generally parallel fashion. Ends 150 of the tubes
are inserted into openings 148 so that fluid may flow from the
manifold into flow paths within the tubes. During insertion of the
tubes within the manifold, leading edge 140 and trailing edge 142
may be determined by the orientation of the tubes. In certain
manufacturing processes, the leading edge and trailing edge may be
marked on the tube using a process such as stamping allowing the
leading edge and trailing edge of each tube to be lined up in
parallel during insertion. Fins 136 may then be inserted between
the tubes 124 to promote heat transfer between an external fluid,
such as air or water, and the refrigerant flowing within the
tubes.
FIG. 9 illustrates a temperature profile 152 for a multichannel
tube 124 that is included in a condenser. Temperature profile 152
depicts the change in temperature across width A of multichannel
tube 124. An x-axis 154 represents the distance across tube width
A, and a y-axis 156 represents the temperatures of the refrigerant
within tube 124 and the external fluid flowing across tube 124. The
temperature of the external fluid is represented by air temperature
158, and the temperature of the refrigerant is represented by
condensing temperature 160. At leading edge 140, air temperature
158 is much lower than condensing temperature 160. As the air flows
across width A, the air is heated by heat received from refrigerant
flowing within tube 124. Consequently, the temperature of the air
increases across width A so that at trailing edge 142 air
temperature 158 is greater than it was at leading edge 140. Note
that condensing temperature 160 has remained fairly constant
causing a temperature difference 162, indicated generally by the
shaded area, to decrease across width A. Temperature difference 162
represents the temperature difference between condensing
temperature 160 air temperature 158. Because heat transfer is a
function of the temperature difference 162, more heat transfer may
occur near leading edge 140 where the temperature difference 162 is
greater.
FIG. 9 also illustrates the internal configuration of flow paths
144 across width A of tube 124. The internal configuration is
intended to maximize heat transfer for temperature profile 152.
Flow paths 144 are spaced apart at a constant spacing C with the
size of the flow paths decreasing across width A in the direction
of air flow 138. Flow paths 164 are located near leading edge 140
and have a first size illustrated by a radius D. Flow paths 166 are
located farther from leading edge 140 and have a second size,
illustrated by a radius E. Note that radius E is smaller than
radius D, resulting in flow paths 166 having a smaller flow area
than flow paths 164. Flow paths 168 are located farthest from
leading edge 140 and have a third size, illustrated by a radius F.
Radius F is the smallest of the radii D, E, and F, resulting in
flow paths 168 having the smallest flow area within tube 124.
Consequently, as the flow paths 164, 166, and 168 are located
farther away from leading edge 140, the size of the flow paths, and
consequently, the flow area within the flow paths, decreases. Flow
paths 164, located closest to leading edge 140, have the largest
flow area and, thus, are able to accommodate the highest amount of
refrigerant while flow paths 168, located farthest from leading
edge 140, have the smallest flow area, and thus, are able to
accommodate the least amount of refrigerant flow. Thus, the tube is
configured to allow more refrigerant to flow near leading edge 140
where temperature difference 162 is the greatest.
FIG. 10 illustrates a temperature profile 170 for multichannel tube
124 when it is used in a heat exchanger functioning as an
evaporator. Temperature profile 170 depicts the changing
temperature across width A of tube 124. X-axis 154 represents the
distance across width A, and y-axis 156 represents the temperature
of the refrigerant and the external fluid, which in this case is
air. Temperature difference 162, shown by the hatched area,
represents the temperature difference between the air flowing over
tube 124 and the refrigerant flowing within tube 124. Because tube
124 is located in an evaporator, an evaporation temperature 172
represents the temperature of the refrigerant. The temperature of
the air is represented on temperature profile 170 as air
temperature 158. As air, shown generally by arrow 138, flows across
tube 124, the temperature of the air decreases to approach
evaporation temperature 172. For example, as shown on temperature
profile 170, air flow 138 first contacts leading edge 140 when air
temperature 158 is much higher than evaporation temperature 172. As
the air flows across width A, the air releases heat to the
refrigerant flowing within the tube. Consequently, the air is
cooled to a temperature that decreases across the width A. As
illustrated by temperature profile 170, air temperature 158 at
trailing edge 142 is much lower than air temperature 158 at leading
edge 140. Evaporation temperature 172 remains relatively constant
across width A. Because air temperature 158 approaches evaporation
temperature 172 as the air flows across width A, temperature
difference 162 decreases across width A. Consequently, more heat
transfer may occur at leading edge 140, where the temperature
difference is the greatest, than at trailing edge 142, where the
temperature difference is the smallest.
As illustrated by FIGS. 9 and 10, the same internal tube
configuration may be used in both a condenser and an evaporator.
The tube configuration employed in FIG. 10 is the same tube
configuration employed in FIG. 9. In FIG. 10, flow paths 164, which
are located closest to leading edge 140, have the largest radius,
and consequently the largest flow area, allowing more refrigerant
to flow near leading edge 140. As flow paths 164, 166, and 168 are
located farther from the leading edge 140, their size decreases.
For example, flow paths 168 are located closest to trailing edge
142 and have the smallest radius F, resulting in the smallest
amount of fluid flow occurring near trailing edge 142. When tube
124 is used in a condenser (FIG. 9) and when tube 124 is used in an
evaporator (FIG. 10), leading edge 140 is the edge of the tube
closest to the largest flow paths. The consistency of the leading
edge location between condensers and evaporators allows the tubes
to be marked during manufacturing to specify the leading edge and
the trailing edge. Although flow paths of three different size are
depicted in FIGS. 9 and 10, the number of different size flow paths
within a tube may vary. For example, according to exemplary
embodiments, flow paths of five different sizes may be provided.
Furthermore, the number of flow paths of each size may vary based
on specific properties of the heat exchanger, such as the
refrigerant used, the location of the heat exchanger, the tube
surface area, and the fin height.
FIGS. 11 through 16 depict alternate flow path configurations for
the multichannel tubes. These figures illustrate exemplary
cross-sectional shapes for flow paths, exemplary spacing that may
be used between the flow paths, and exemplary sizes that may be
employed for the flow paths. It should be noted, however, that the
shapes and spacing shown throughout the figures are not intended to
be limiting, and other optimized shapes, sizes, spacings, and
combinations thereof may be provided.
FIG. 11 illustrates an alternate tube 174 with flow paths
configured to concentrate flow near leading edge 140. Each of the
flow paths 176, 178, 180 are spaced apart at a constant spacing G.
However, the size of flow paths 176, 178, and 180 decreases across
width A to concentrate flow near leading edge 140. For example,
flow paths 176 are located nearest to leading edge 140 and have an
oblong shaped opening of a height H and a length J. The oblong
shape allows a relatively large amount of flow through flow paths
176. Flow paths 178 are disposed towards the middle of the tube and
have a circular cross-section of a radius K. Flow paths 178 have a
smaller cross-sectional area than flow paths 176. Flow paths 180
are located closest to trailing edge 142 and have a circular
cross-section of a radius L that is smaller than radius K. Flow
paths 180 have the smallest cross-section area and, therefore,
allow for the least amount of flow.
FIG. 12 illustrates another alternate tube 182 with flow paths
configured to concentrate flow near the leading edge of the tube.
All of the flow paths 184, 186, 188, and 190 are spaced apart at a
constant spacing M. However, flow paths 184, 186, 188, and 190 each
have a different cross-sectional size and shape that decreases as
the flow paths are located closer to trailing edge 142. Flow paths
184 are located closest to leading edge 140 and have a circular
shaped opening with a relatively large cross-sectional area. Flow
paths 186 are disposed near the middle of the tube and have a
square shaped opening with a cross-sectional area smaller than the
cross-sectional area of flow paths 184. Flow paths 188 are located
to the right of flow paths 186 and have an even smaller
cross-sectional area. Flow paths 188 have a bow-tie shaped
cross-section of a size similar to the square shaped opening of
flow paths 186; however, the center portions of the square on the
top and bottom have been indented to reduce the cross-sectional
area of these flow paths. The indentations also may function to
increase the frictional pressure drop for these flow paths. Flow
path 190 is located closest to the trailing edge and is of the
smallest cross-sectional area. The outer cross-section has a size
similar to the square shaped openings of flow paths 186; however,
flow path 190 has indentations that indent inwards from all four
sides of the square and extend throughout the length of the flow
path. The indentations are intended to decrease the cross-sectional
area of flow path 190 and increase the frictional pressure drop of
flow path 190. Flow paths 184, 186, 188, and 190 each have openings
of a different shape that is intended to decrease the
cross-sectional area of flow paths 184, 186, 188, and 190 across
width A from leading edge 140 to trailing edge 142. Consequently,
more refrigerant flows within tube 182 near leading edge 140 where
temperature difference 162 (see FIGS. 9 and 10) is the
greatest.
FIG. 13 illustrates another alternate tube configuration 192 that
includes flow paths 194 of a constant size illustrated by a radius
N. Instead of varying the size of the flow paths as shown in FIGS.
9 through 12, the spacing between flow paths 194 has been increased
progressively towards trailing edge 142. The increased spacing is
intended to concentrate flow near leading edge 140 while utilizing
flow paths of a constant size N. The flow paths disposed near
leading edge 140 are spaced apart at a first spacing P. The flow
paths located near the center of the tube are disposed apart at a
distance Q that is greater than distance P. The flow path closest
to trailing edge 142 is spaced apart at a distance R that is
greater than distances P and Q. Although three distances P, Q, and
R are shown in FIG. 13, any number of distances may be used for the
spacing between the flow paths. For example, according to an
exemplary embodiment, four different spacings may be used, each of
which is twice the spacing of the previous spacing located toward
the leading edge.
The progressively decreasing spacing shown in FIG. 13 also may be
used with flow paths of various cross-sectional shapes. For
example, FIG. 14 illustrates flow paths 198 that have a rectangular
shaped cross-section of a constant size defined by a height S and a
width T. The spacing between flow paths 198 increases as the flow
paths are located closer to trailing edge 142. The flow path
disposed near the leading edge 140 is spaced apart at a distance U.
The flow paths located near the center of the tube are spaced apart
at a distance V that is twice distance U. The next flow path
towards the trailing edge is spaced apart at a distance W, and the
flow path disposed closest to trailing edge 142 is spaced apart at
a distance X. Distances U, V, W, and X increase across the width
from leading edge 140 to trailing edge 142. Consequently, more flow
paths are located near leading edge 140 to allow more refrigerant
to flow near leading edge 140.
FIGS. 15 and 16 illustrate alternate tube configurations that vary
both the size of the flow paths and the spacing across the tube
width. In general, the spacing increases and the size decreases
from leading edge 140 to trailing edge 142. FIG. 15 illustrates an
alternate tube 200 with flow paths of a circular cross-section that
decrease in size. Flow paths 202 have a first cross-sectional area
illustrated by radius Y and are spaced apart at a distance AB. Flow
paths 204 are disposed near the center of the tube and have a
smaller cross-sectional area illustrated by a radius Z. Flow paths
204 are spaced apart at a distance AC that is greater than distance
AB. The greater distance AC between flow paths 204 and the smaller
cross-sectional area results in less flow near the center of the
tube than near leading edge 140. Flow paths 206 are disposed
nearest to trailing edge 142 and have the smallest cross-sectional
area illustrated by radius AA. Flow paths 206 are spaced apart at
the largest distance AD. Both the increased spacing between the
flow paths and the decreased size of the flow paths is intended to
concentrate flow near leading edge 140.
FIG. 16 illustrates another alternate tube 208 that employs not
only increased spacing between flow paths and decreased size of the
flow paths, but also varying cross-sectional shapes of the flow
paths. A flow path 210 is located nearest leading edge 140 and has
an oblong shape that yields the largest cross-sectional area of the
flow paths within tube 208. Flow path 210 is spaced apart from a
flow path 212 at a distance AE. Distance AE is the smallest
distance employed within tube 208. To the right of flow path 210
are two flow paths 212 of circular cross-sections that provide a
smaller cross sectional area than flow path 210. Flow paths 212 are
spaced apart at a distance AF that is slightly larger than distance
AE. To the right of flow paths 212 is a flow path 214 of a square
cross-section that is smaller than the cross-sections of flow paths
212. Flow path 214 is space apart at a distance AG that is larger
than distance AF. To the right of flow path 214 is a flow path 216
of a bow-tie cross-section that is smaller than the cross-sectional
area of preceding flow path 214. Flow path 216 is spaced apart at a
distance AF that is greater than the previous distances AE, AF, and
AG. Finally, a flow path 218 is located nearest trailing edge 142.
Flow path 218 has the smallest cross-section and includes
indentations along the top, bottom, right and left sides of the
opening. Flow path 218 is spaced apart at the greatest spacing AI.
The increasing spacing, varying shapes, and decreasing
cross-sectional areas are intended to concentrate flow near leading
edge 140.
FIGS. 9 through 16 illustrate tube configurations for concentrating
refrigerant flow near the leading edge of the tubes by varying the
spacing between the flow paths, the flow path shapes, and the
cross-sectional areas. These configurations may be employed when
the tubes are extruded, or formed, during the manufacturing
process. For example, the different size and shape flow paths may
be created during manufacturing by an extrusion process where
different extrusion dies are used to form the flow paths. According
to exemplary embodiments, the tubes may be stamped, or marked,
during manufacture to identify the leading edge and/or the trailing
edge.
FIGS. 17 through 28 illustrate tube configurations for favoring
flow near the leading edge that can be employed either during the
manufacture process or after manufacture by modifying existing
tubes. FIG. 17 illustrates an alternate tube 220 with flow paths
144 spaced apart at a constant spacing AJ. Each of the flow paths
has a constant size illustrated by openings 224. Air flow 138
passes over the tube from leading edge 140 to trailing edge 142.
Inserts 222 may be inserted into openings 224 located near trailing
edge 142 to reduce their size. Inserts 122 are intended to reduce
the size of the flow paths disposed near trailing edge 142 so that
flow is concentrated near leading edge 140. According to exemplary
embodiments, inserts 222 may be inserted into the tube during
manufacturing and joined to the tubes through a process such as
brazing or other joining process. According to alternate exemplary
embodiments, an existing tube may be modified by placing inserts
222 within the flow paths. The number of flow paths containing
inserts may vary depending on specific heat exchanger properties
such as the refrigerant used, the flow rate within the tube, and
the number of flow paths within the tube. The number of flow paths
containing inserts also may vary between tubes within a heat
exchanger. For example, in a heat exchanger where tubes located
near the bottom receive less air flow, a greater number of inserts
may be used in the bottom tubes.
The inserts may be placed in either end of the tube. However,
according to a presently contemplated embodiment, the inserts may
be placed in the end of the tube containing the lowest vapor
quality, that is, the end of the tube containing the lowest ratio
of vapor in the refrigerant. For example, in an evaporator,
refrigerant typically may enter the tube in the liquid phase. As
the refrigerant flows through the length of the tube, it absorbs
heat from the hot air flowing over the tube and the liquid changes
into a vapor phase. Consequently, the inlet side of the tube
contains the most liquid and thus the lowest vapor quality.
Therefore, in tubes for use in a heat exchanger functioning as an
evaporator, the inserts may be inserted at the inlet side of the
tubes. On the other hand, in a condenser, refrigerant enters the
tubes primarily in the vapor phase. The refrigerant vapor is cooled
by the cool air flowing over the tubes, which causes the vapor
condense into a liquid. Consequently, in a condenser, the outlet
side of the tube contains the most amount of liquid and therefore
has the lowest vapor quality. As a result, the inserts may be
placed in the outlet side of the tube flow paths for a
condenser.
FIG. 18 is a detailed perspective view of an insert 222 used in
FIG. 17. Insert 222 includes a body 226 of a length AK. When
inserted, body 226 extends into the flow paths of the multichannel
tube. Insert 222 also includes a head 228 that has a cross-section
that is larger than the flow path openings. Due to its relatively
larger size, head 228 protrudes from the flow path openings 224
(shown in FIG. 17). Head 228 also provides support for insert 222
and prevents insert 222 from sliding too far into the flow path.
Head 228 includes an opening 230 adjoining a path 232 extending
through body 226. Path 232 allows flow of refrigerant within insert
222 and has a radius AL that is smaller than the flow path
openings. The smaller radius reduces the flow area when the insert
is inserted within the flow path. Length AK and radius AL may vary
depending on how much flow restriction is needed in a multichannel
tube. The insert may be constructed of aluminum or other suitable
material brazed or otherwise joined to the flow paths.
FIG. 19 illustrates an alternate insert 234 that may be inserted
into flow paths of a multichannel tube. Insert 234 includes a body
236, a head 238, and a tapered end 240. Tapered end 240 facilitates
insertion into a flow path. Head 238 is of a larger cross-sectional
size than the flow path, allowing insert 234 to protrude from the
flow path, while a portion of the body 236 is inserted into the
flow path to restrict the size of the flow path. Body 236 has a
length AM that may be inserted into the flow path. However,
according to exemplary embodiments, the entire length may not fit
within the flow path. Tapered end 240 allows a common insert to be
used for various flow path sizes where the insert will be inserted
by varying amounts depending on the size of the flow path opening.
Insert 234 contains an opening 242 that is smaller than the flow
path opening to allow reduction of the flow path size. A path 244
extends from opening 242 to the end of the insert to allow flow of
refrigerant within the insert. Although FIGS. 19 and 20 depict
inserts of circular cross-sections, the inserts may have any shape
cross-section that fits within the flow paths. For example, inserts
of a square shaped cross-section may be inserted into flow paths of
a square shaped cross-section.
FIG. 20 illustrates an alternate tube configuration 245 employing
insert 234. A mounting bracket 246 may be used to place inserts 234
within flow paths 144. According to exemplary embodiments, the
bracket may be constructed of aluminum and may be brazed or
otherwise joined to the inserts prior to insertion into the flow
paths. The bracket may provide alignment and stability for the
inserts during insertion. Bracket 246 includes a rear surface 248
that may be disposed on a front surface 250 of the tube. The
bracket may be permanently affixed to the inserts and joined to the
tube when the inserts are inserted into the flow paths. However,
according to other exemplary embodiments, the bracket may be
removable from the inserts after the inserts are placed within the
flow paths.
FIG. 21 is a detailed perspective view of bracket 246. Bracket 246
includes grooves 252 that provide a recess for the inserts. Grooves
252 may provide stability and facilitate alignment of the inserts
during placement within the flow paths. The bracket may be used
with alternate insert 234 as well as with insert 222 illustrated in
FIG. 18.
FIG. 22 illustrates an alternate tube configuration 254 employing a
plate 256 for varying the size of the flow paths 144 to promote
flow near leading edge 140. To vary the size of flow paths 144,
plate 256 may be brazed or otherwise joined to the tube in a manner
that overlaps with some of the flow paths 144. A rear surface 258
of the plate may be attached to a front surface 260 of the tube.
Plate 256 includes openings 262 of different sizes and spacings
that vary from the size and spacing of flow path openings 264. For
example, a larger opening may be placed over the tube near leading
edge 140 to encircle multiple flow channels and allow flow through
the entire cross-section of these flow channels while smaller
openings may be placed over the tube near trailing edge 142 to
overlap with flow channels and reduce the cross-sectional area for
flow. As shown, plate 256 may be used with a tube that has flow
paths 144 of a constant size that are spaced apart at a constant
spacing AP. However, according to other exemplary embodiments, the
plate may be employed with the internal tube configurations of
varying spacing, cross-sections, and size, such as those
illustrated in FIGS. 16 through 19. Although the plate may be
inserted over either end of the tube, in a presently contemplated
embodiment, the plate may be inserted over the end of the tube
containing the lowest vapor quality.
FIG. 23 depicts tube configuration 254 with plate 256 disposed
against the tube. A first opening 264 on the plate covers the first
two flow paths 264 disposed closest to leading edge 140. The
relatively large size of opening 264 allows the entire area of the
first two flow paths to be used for flowing refrigerant within the
tube near leading edge 140. Plate 256 also includes second openings
268 that do not align with individual flow path openings 264.
Although second openings 268 are relatively the same size as flow
path openings 264, second openings 268 are centered between
openings 264 so that second openings 268 partially obstruct flow
path openings 264 to reduce the cross-sectional area available for
refrigerant flow. Plate openings 262, 266, and 268 are spaced apart
at a distance AQ that allows plate openings 262, 266, and 268 to
overlap with, but not completely align with, flow path openings
264. As shown by the dashed lines, several flow path openings 264
are partially obstructed by plate 256. The obstructed openings are
located generally nearer to trailing edge 142 while the
unobstructed openings are located generally nearer to leading edge
140. Consequently, the openings nearer to trailing edge 142 have a
reduced cross-sectional area available for flow resulting in a tube
configuration that promotes flow near leading edge 140. Although
two different sizes of openings are shown in FIG. 23, the plate may
have any number of openings of various sizes. For example, the
plate may have openings that align directly with flow paths near
the leading edge, while the openings near the trailing edge are
smaller than the flow path openings.
A plate also may be used to customize multichannel tubes containing
flow paths configured to promote flow near the leading edge such as
those shown in FIGS. 9 through 16. FIG. 24 illustrates an alternate
configuration 270 where a plate 272 is used to customize a tube 124
containing flow paths 274, 276, and 278 of different sizes and
cross-sections. Flow paths 274, 276 and 278 are configured to
promote refrigerant flow near leading edge 140. Flow paths 274 are
located near leading edge 140 and are of a circular cross-section
and a relatively large size. Flow paths 276 are disposed near the
middle of the tube and are also of a circular cross-section, but of
a smaller size than first flow paths 274. Third flow paths 278 are
located closest to trailing edge 142 and are of a rectangular shape
and a relatively small size. Plate 272 includes openings 280, 282,
and 290 that are configured to allow refrigerant to pass through
plate 272 into flow paths 274, 276, and 278. First opening 280 is
aligned to allow refrigerant to flow into the first four flow paths
274. Second opening 282 is aligned to allow refrigerant to flow
into second flow paths 276. Third opening 290 is aligned to
partially obstruct third flow paths 278 so that refrigerant may
flow through only a portion of these flow paths. Plate openings
280, 282, and 290 are configured to promote flow near leading edge
140 by partially obstructing flow paths 274 that are located
closest to trailing edge 142. According to other exemplary
embodiments, the plate may contain any number of openings of
various sizes and spacing configured to align with and/or partially
obstruct flow paths.
FIG. 25 illustrates an alternate configuration 292 employing an
alternate plate 294 designed to partially obstruct specific flow
paths. Plate 294 increases progressively in height across width A
from a relatively small height AS disposed near leading edge 140
and a relatively large height AT disposed near trailing edge 142.
The progressively increasing height allows plate 294 to obstruct
flow paths 144 by an amount that increases progressively from
leading edge 140 to trailing edge 142. In this manner, the flow
paths located near leading edge 140 remain partially or completely
unobstructed while the flow paths located near trailing edge 142
are more obstructed to promote flow near leading edge 140. Plate
294 may be used with tubes including flow paths of a constant size,
cross-section and spacing as shown in FIG. 25, as well as with
tubes of various cross-sections, spacing and sizes as previously
illustrated in FIGS. 9 through 16. Furthermore, heights AS and AT
of the plate may vary based on the amount of obstruction required.
Although plate 294 is shown in FIG. 25 as being aligned with the
top of the tube, according to other exemplary embodiments, the
plate may be aligned with the bottom of the tube.
FIG. 26 illustrates an alternate configuration 296 that may be used
to promote fluid flow near leading edge 140. Instead of a plate as
shown in FIGS. 22 through 25, a sleeve 298 may be placed over an
end 300 of the tube. Sleeve 298 encapsulates an outer portion of
the tube and may provide additional stability and a solid joint
between sleeve 298 and the tube. Sleeve 298 includes an interior
volume 301 that may be hollow to allow sleeve 298 to enclose the
outside of the tube. A front surface 302 may contain openings 304
that allow flow of refrigerant through sleeve 298 and into flow
path openings 306 contained within the tube. Sleeve openings 304
may be configured to align with and partially obstruct some of the
flow path openings 306 to promote flow near leading edge 140.
Sleeve 298 includes a length AU that determines the amount of
overlap between sleeve 298 and the tube. For example, as length AU
increases, sleeve 298 will encapsulate more of the tube. Length AU
may vary depending on the support needed for the sleeve. The sleeve
may be constructed of aluminum or other suitable material and may
be placed loosely over the tube or brazed or joined to the tube.
Front surface 302 may contain openings of various configurations
such as those illustrated by the plates shown in FIGS. 22 through
25. According to certain exemplary embodiments, the openings may be
of varying cross-sections, spacings, and sizes to promote fluid
flow near the leading edge.
FIGS. 27 and 28 illustrate alternate configurations for promoting
flow near the leading edge where sections of the tube operate as
flow control mechanisms. FIG. 27 illustrates an alternate tube 308
containing a crimped section 310. In crimped section 310,
indentations 312 have been made into flow paths 144 to convert the
flow paths from original flow paths 314 into crimped flow paths
316. The tube includes original flow paths 314 located near leading
edge 140 that have a square cross-section. Crimped flow paths 316
are located near trailing edge 142 and include indentations 312
that create a bow-tie shaped cross-section. The bow-tie shaped
cross section provides a smaller cross-section and flow area for
crimped flow paths 316 than for original flow paths 314. The
smaller cross-section and flow area are designed to promote more
refrigerant flow within original flow paths 314, which are nearer
to leading edge 140. The bow-tie shaped cross-section extends
through tube for a length AV. According to certain exemplary
embodiments, length AV may extend the entire length of the tube.
However, according to other exemplary embodiments, length AV may
extend for only a portion of the tube. In a presently contemplated
embodiment, length AV may extend within a portion of the tube near
the low vapor quality end of the tube. As may be appreciated, the
low vapor quality end of the tube may vary depending on whether the
tube is located in a heat exchanger functioning as an evaporator or
as a condenser. For example, in an evaporator, the inlet side of
the tube contains the most liquid and thus the lowest vapor
quality. Therefore, in an evaporator, the length AV may extend near
the inlet side of the tube. In a condenser, the outlet side of the
tube contains the most liquid, and therefore has the lowest vapor
quality. As a result, in a condenser, the length AV may extend near
the outlet side of the tube.
The crimped section may be produced during manufacturing of the
tube, or an existing tube may be modified by crimping to customize
a tube already manufactured and/or contained within a heat
exchanger. The crimped section may be formed using a tool, such as
die press or the like, to produce indentations within the flow
paths. The angle of the indentations may vary depending on the size
reduction required to promote flow near the leading edge.
FIG. 28 depicts an alternate tube 318 containing a crushed section
320 that promotes flow near leading edge 140. Tube 318 includes
original flow paths 322 and crushed flow paths 324 contained within
a crushed section 320. Original flow paths 322 have a larger
cross-section than the crushed flow paths 324. In crushed section
320, a portion of the tube extending for a length AW has been
pressed or flattened to reduce the size of crushed flow paths 324.
According to certain exemplary embodiments, the crushed section may
extend the entire length of the tube; while according to other
exemplary embodiments, the crushed section may extend for a length
AW located hear the low vapor quality end of the tube. Crushed
section 320 functions to reduce the height of the tube from the
unmodified height AY to a reduced height AZ. Reduced height AZ may
vary depending on the individual properties of the heat exchanger.
The width AX that has been crushed may vary depending on the
desired number of crushed openings 324. Crushed section 320
produces crushed flow paths 324 that become increasingly smaller in
size as they approach the trailing edge 142, and is intended to
concentrate flow near leading edge 140.
Any combination of tube configurations may be used in accordance
with the present techniques to promote flow near the leading edge
of a tube. For example, tubes may contain flow paths of various
sizes, cross-sections, and spacings as illustrated in FIGS. 9
through 16. These tubes may be further modified by using inserts or
blocking plates or sleeves shown in FIGS. 17 through 26. According
to certain exemplary embodiments, tubes containing flow paths of a
constant size and spacing, such as the tube illustrated in FIG. 22,
may be modified by a blocking plate or sleeve as illustrated in
FIGS. 22 through 26. According to other exemplary embodiments,
tubes of a constant cross-section and spacing may be crimped or
crushed to provide a flow control mechanism contained within a
section of the tube. The modifications performed on the tube or the
configurations employed may vary depending on the individual
properties of the heat exchanger.
The tube configurations described in FIGS. 9 through 28 may find
application in a variety of heat exchangers and HVAC&R systems
containing heat exchangers. However, the configurations are
particularly well-suited to heat exchangers functioning as
evaporators and/or condensers where the temperature difference
between the refrigerant and the external fluid is much greater at
the leading edge of the tubes than at the trailing edge of the
tubes. The tube configurations are intended to promote flow of
refrigerant near the leading edge to capitalize on the large
temperature difference that may exist near the leading edge.
It should be noted that the present discussion makes use of the
term "multichannel" tubes or "multichannel heat exchanger" to refer
to arrangements in which heat transfer tubes include a plurality of
flow paths between manifolds that distribute flow to and collect
flow from the tubes. A number of other terms may be used in the art
for similar arrangements. Such alternative terms might include
"microchannel" and "microport." The term "microchannel" sometimes
carries the connotation of tubes having fluid passages on the order
of a micrometer and less. However, in the present context such
terms are not intended to have any particular higher or lower
dimensional threshold. Rather, the term "multichannel" used to
describe and claim embodiments herein is intended to cover all such
sizes. Other terms sometimes used in the art include "parallel
flow" and "brazed aluminum". However, all such arrangements and
structures are intended to be included within the scope of the term
"multichannel." In general, such "multichannel" tubes will include
flow paths disposed along the width or in a plane of a generally
flat, planar tube, although, again, the invention is not intended
to be limited to any particular geometry unless otherwise specified
in the appended claims.
While only certain features and embodiments of the invention have
been illustrated and described, many modifications and changes may
occur to those skilled in the art (e.g., variations in sizes,
dimensions, structures, shapes and proportions of the various
elements, values of parameters (e.g., temperatures, pressures,
etc.), mounting arrangements, use of materials, colors,
orientations, etc.) without materially departing from the novel
teachings and advantages of the subject matter recited in the
claims. The order or sequence of any process or method steps may be
varied or re-sequenced according to alternative embodiments. It is,
therefore, to be understood that the appended claims are intended
to cover all such modifications and changes as fall within the true
spirit of the invention. Furthermore, in an effort to provide a
concise description of the exemplary embodiments, all features of
an actual implementation may not have been described (i.e., those
unrelated to the presently contemplated best mode of carrying out
the invention, or those unrelated to enabling the claimed
invention). It should be appreciated that in the development of any
such actual implementation, as in any engineering or design
project, numerous implementation specific decisions may be made.
Such a development effort might be complex and time consuming, but
would nevertheless be a routine undertaking of design, fabrication,
and manufacture for those of ordinary skill having the benefit of
this disclosure, without undue experimentation.
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